Sensor Array with Edge Pattern

ABSTRACT

A capacitive sensor array may include a first set of sensor electrodes and a second set of sensor electrodes. Each of the second set of sensor electrodes may intersect each of the first set of sensor electrodes to form a plurality of unit cells each corresponding to a pair of sensor electrodes including one of the first set of sensor electrodes and one of the second set of sensor electrodes. Each point within each of the plurality of unit cells may nearer to a gap between the pair of sensor electrodes corresponding to the unit cell than to a gap between any different pair of sensor electrodes, and a first trace pattern within a first unit cell of the plurality of unit cells may be different from a second trace pattern within an adjacent unit cell of the plurality of unit cells.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/631,369, filed on Sep. 28, 2012, which claims priority to U.S.Provisional Application No. 61/672,992, filed on Jul. 18, 2012, which ishereby incorporated by reference.

TECHNICAL FIELD

This disclosure relates to the field of touch-sensors and, inparticular, to trace patterns of electrodes in capacitive touch-sensorarrays.

BACKGROUND

Computing devices, such as notebook computers, personal data assistants(PDAs), kiosks, and mobile handsets, have user interface devices, whichare also known as human interface devices (HID). One user interfacedevice that has become more common is a touch-sensor pad (also commonlyreferred to as a touchpad). A basic notebook computer touch-sensor pademulates the function of a personal computer (PC) mouse. A touch-sensorpad is typically embedded into a PC notebook for built-in portability. Atouch-sensor pad replicates mouse X/Y movement by using two defined axeswhich contain a collection of sensor electrodes that detect the positionof one or more conductive objects, such as a finger. Mouse right/leftbutton clicks can be replicated by two mechanical buttons, located inthe vicinity of the touchpad, or by tapping commands on the touch-sensorpad itself. The touch-sensor pad provides a user interface device forperforming such functions as positioning a pointer, or selecting an itemon a display. These touch-sensor pads may include multi-dimensionalensor arrays for detecting movement in multiple axes. The sensor arraymay include a one-dimensional sensor array, detecting movement in oneaxis. The sensor array may also be two dimensional, detecting movementsin two axes.

Another user interface device that has become more common is a touchscreen. Touch screens, also known as touchscreens, touch windows, touchpanels, or touchscreen panels, are transparent display overlays whichare typically either pressure-sensitive (resistive or piezoelectric),electrically-sensitive (capacitive), acoustically-sensitive (surfaceacoustic wave (SAW)) or photo-sensitive (infra-red). The effect of suchoverlays allows a display to be used as an input device, removing thekeyboard and/or the mouse as the primary input device for interactingwith the display's content. Such displays can be attached to computersor, as terminals, to networks. Touch screens have become familiar inretail settings, on point-of-sale systems, on ATMs, on mobile handsets,on kiosks, on game consoles, and on PDAs where a stylus is sometimesused to manipulate the graphical user interface (GUI) and to enter data.A user can touch a touch screen or a touch-sensor pad to manipulatedata. For example, a user can apply a single touch, by using a finger totouch the surface of a touch screen, to select an item from a menu.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings.

FIG. 1 is a block diagram illustrating an embodiment of an electronicsystem that processes touch sensor data.

FIG. 2 is a block diagram illustrating an embodiment of an electronicsystem that processes touch sensor data.

FIG. 3A illustrates an embodiment of an electronic touch-sensing systemusing a dual solid diamond capacitive sensor pattern.

FIG. 3B illustrates an embodiment of a dual solid diamond capacitivesensor pattern.

FIG. 4A illustrates an embodiment of a capacitive sensor array.

FIG. 4B illustrates an embodiment of a capacitive sensor array.

FIG. 5 illustrates an embodiment of a capacitive sensor array.

FIG. 6 illustrates an embodiment of a capacitive sensor array.

FIGS. 7A-7N illustrate various embodiments of trace patterns for asensor electrode of a capacitive sensor array.

FIG. 8 illustrates a corner portion of a capacitive sensor array,according to an embodiment.

FIG. 9 illustrates a corner portion of a capacitive sensor array,according to an embodiment.

FIGS. 10A-10C illustrate embodiments of a capacitive sensor array.

FIGS. 11A and 11B illustrate embodiments of capacitive sensor arrayshaving a diamond patterns.

FIG. 12 illustrates an embodiment of a capacitive sensor array having a“totem pole” pattern.

DETAILED DESCRIPTION

The following description sets forth numerous specific details such asexamples of specific systems, components, methods, and so forth, inorder to provide a good understanding of several embodiments of thepresent invention. It will be apparent to one skilled in the art,however, that at least some embodiments of the present invention may bepracticed without these specific details. In other instances, well-knowncomponents or methods are not described in detail or are presented in asimple block diagram format in order to avoid unnecessarily obscuringthe present invention. Thus, the specific details set forth are merelyexemplary. Particular implementations may vary from these exemplarydetails and still be contemplated to be within the spirit and scope ofthe present invention.

In one embodiment, a capacitive sensor array having intersecting row andcolumn sensor electrodes may be constructed such that the electrodeshave a different pattern of conductive material in a first region thanin a second region. For example, a region that includes the corners andedges of the sensor array may have a different pattern than a regionthat includes the core of the sensor array.

In one embodiment, each region may be composed of a number of unitcells, which each correspond to a pair of sensor electrodes including arow sensor electrode and a column sensor electrode. The unit cell thusidentifies an area of the capacitive sensor array where the mutualcapacitance between the pair of electrodes may be affected by a fingeror other conductive object proximate to the surface of the sensor array.In one embodiment, the pattern of conductive material making up theportions of the sensor electrodes within one of the unit cells in afirst region may differ from a pattern of conductive material making upportions of the sensor electrodes within an adjacent unit cell in adifferent region.

In one embodiment, a capacitance sensor coupled with a capacitive sensorarray as described above may be used to scan the capacitive sensor arrayby measuring the self capacitances associated with each sensorelectrode, or the mutual capacitances between pairs of sensorelectrodes. The capacitance sensor may then transmit the measuredcapacitance values to a host, where the capacitance values may befurther processed to determine, for example, locations of fingers orother conductive objects near or touching the surface of the capacitivesensor array. In one embodiment, the host compensates for thecapacitance differences between the regions having different patterns ofconductive traces.

FIG. 1 illustrates a block diagram of one embodiment of an electronicsystem 100 including a processing device 110 that may be configured tomeasure capacitances from a touch sensing surface 116 including acapacitive sensor array as described above. The electronic system 100includes a touch-sensing surface 116 (e.g., a touchscreen, or a touchpad) coupled to the processing device 110 and a host 150. In oneembodiment, the touch-sensing surface 116 is a two-dimensional userinterface that uses a sensor array 121 to detect touches on the surface116.

In one embodiment, the sensor array 121 includes sensor electrodes121(1)-121(N) (where N is a positive integer) that are disposed as atwo-dimensional matrix (also referred to as an XY matrix). The sensorarray 121 is coupled to pins 113(1)-113(N) of the processing device 110via one or more analog buses 115 transporting multiple signals. In thisembodiment, each sensor electrode 121(1)-121(N) is represented as acapacitor.

In one embodiment, the capacitance sensor 101 may include a relaxationoscillator or other means to convert a capacitance into a measuredvalue. The capacitance sensor 101 may also include a counter or timer tomeasure the oscillator output. The processing device 110 may furtherinclude software components to convert the count value (e.g.,capacitance value) into a sensor electrode detection decision (alsoreferred to as switch detection decision) or relative magnitude. Itshould be noted that there are various known methods for measuringcapacitance, such as current versus voltage phase shift measurement,resistor-capacitor charge timing, capacitive bridge divider, chargetransfer, successive approximation, sigma-delta modulators,charge-accumulation circuits, field effect, mutual capacitance,frequency shift, or other capacitance measurement algorithms. It shouldbe noted however, instead of evaluating the raw counts relative to athreshold, the capacitance sensor 101 may be evaluating othermeasurements to determine the user interaction. For example, in thecapacitance sensor 101 having a sigma-delta modulator, the capacitancesensor 101 is evaluating the ratio of pulse widths of the output,instead of the raw counts being over or under a certain threshold.

In one embodiment, the processing device 110 further includes processinglogic 102. Operations of the processing logic 102 may be implemented infirmware; alternatively, it may be implemented in hardware or software.The processing logic 102 may receive signals from the capacitance sensor101, and determine the state of the sensor array 121, such as whether anobject (e.g., a finger) is detected on or in proximity to the sensorarray 121 (e.g., determining the presence of the object), where theobject is detected on the sensor array (e.g., determining the locationof the object), tracking the motion of the object, or other informationrelated to an object detected at the touch sensor.

In another embodiment, instead of performing the operations of theprocessing logic 102 in the processing device 110, the processing device110 may send the raw data or partially-processed data to the host 150.The host 150, as illustrated in FIG. 1, may include decision logic 151that performs some or all of the operations of the processing logic 102.Operations of the decision logic 151 may be implemented in firmware,hardware, software, or a combination thereof. The host 150 may include ahigh-level Application Programming Interface (API) in applications 152that perform routines on the received data, such as compensating forsensitivity differences, other compensation algorithms, baseline updateroutines, start-up and/or initialization routines, interpolationoperations, or scaling operations. The operations described with respectto the processing logic 102 may be implemented in the decision logic151, the applications 152, or in other hardware, software, and/orfirmware external to the processing device 110. In some otherembodiments, the processing device 110 is the host 150.

In another embodiment, the processing device 110 may also include anon-sensing actions block 103. This block 103 may be used to processand/or receive/transmit data to and from the host 150. For example,additional components may be implemented to operate with the processingdevice 110 along with the sensor array 121 (e.g., keyboard, keypad,mouse, trackball, LEDs, displays, or other peripheral devices).

The processing device 110 may reside on a common carrier substrate suchas, for example, an integrated circuit (IC) die substrate, or amulti-chip module substrate. Alternatively, the components of theprocessing device 110 may be one or more separate integrated circuitsand/or discrete components. In one embodiment, the processing device 110may be the Programmable System on a Chip (PSoC™) processing device,developed by Cypress Semiconductor Corporation, San Jose, Calif.Alternatively, the processing device 110 may be one or more otherprocessing devices known by those of ordinary skill in the art, such asa microprocessor or central processing unit, a controller,special-purpose processor, digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA), or other programmable device. In an alternativeembodiment, for example, the processing device 110 may be a networkprocessor having multiple processors including a core unit and multiplemicro-engines. Additionally, the processing device 110 may include anycombination of general-purpose processing device(s) and special-purposeprocessing device(s).

In one embodiment, the electronic system 100 is implemented in a devicethat includes the touch-sensing surface 116 as the user interface, suchas handheld electronics, portable telephones, cellular telephones,notebook computers, personal computers, personal data assistants (PDAs),kiosks, keyboards, televisions, remote controls, monitors, handheldmulti-media devices, handheld video players, gaming devices, controlpanels of a household or industrial appliances, or other computerperipheral or input devices. Alternatively, the electronic system 100may be used in other types of devices. It should be noted that thecomponents of electronic system 100 may include all the componentsdescribed above. Alternatively, electronic system 100 may include onlysome of the components described above, or include additional componentsnot listed herein.

FIG. 2 is a block diagram illustrating one embodiment of a capacitivetouch sensor array 121 and a capacitance sensor 101 that convertschanges in measured capacitances to coordinates indicating the presenceand location of touch. The coordinates are calculated based on changesin measured capacitances relative to the capacitances of the same touchsensor array 121 in an un-touched state. In one embodiment, sensor array121 and capacitance sensor 101 are implemented in a system such aselectronic system 100. Sensor array 220 includes a matrix 225 of N×Melectrodes (N receive electrodes and M transmit electrodes), whichfurther includes transmit (TX) electrode 222 and receive (RX) electrode223. Each of the electrodes in matrix 225 is connected with capacitancesensing circuit 201 through demultiplexer 212 and multiplexer 213.

Capacitance sensor 101 includes multiplexer control 211, demultiplexer212 and multiplexer 213, clock generator 214, signal generator 215,demodulation circuit 216, and analog to digital converter (ADC) 217. ADC217 is further coupled with touch coordinate converter 218. Touchcoordinate converter 218 may be implemented in the processing logic 102.

The transmit and receive electrodes in the electrode matrix 225 may bearranged so that each of the transmit electrodes overlap and cross eachof the receive electrodes such as to form an array of intersections,while maintaining galvanic isolation from each other. Thus, eachtransmit electrode may be capacitively coupled with each of the receiveelectrodes. For example, transmit electrode 222 is capacitively coupledwith receive electrode 223 at the point where transmit electrode 222 andreceive electrode 223 overlap.

Clock generator 214 supplies a clock signal to signal generator 215,which produces a TX signal 224 to be supplied to the transmit electrodesof touch sensor 121. In one embodiment, the signal generator 215includes a set of switches that operate according to the clock signalfrom clock generator 214. The switches may generate a TX signal 224 byperiodically connecting the output of signal generator 215 to a firstvoltage and then to a second voltage, wherein said first and secondvoltages are different.

The output of signal generator 215 is connected with demultiplexer 212,which allows the TX signal 224 to be applied to any of the M transmitelectrodes of touch sensor 121. In one embodiment, multiplexer control211 controls demultiplexer 212 so that the TX signal 224 is applied toeach transmit electrode 222 in a controlled sequence. Demultiplexer 212may also be used to ground, float, or connect an alternate signal to theother transmit electrodes to which the TX signal 224 is not currentlybeing applied. In an alternate embodiment the TX signal 224 may bepresented in a true form to a subset of the transmit electrodes 222 andin complement form to a second subset of the transmit electrodes 222,wherein there is no overlap in members of the first and second subset oftransmit electrodes 222.

Because of the capacitive coupling between the transmit and receiveelectrodes, the TX signal 224 applied to each transmit electrode inducesa current within each of the receive electrodes. For instance, when theTX signal 224 is applied to transmit electrode 222 through demultiplexer212, the TX signal 224 induces an RX signal 227 on the receiveelectrodes in matrix 225. The RX signal 227 on each of the receiveelectrodes can then be measured in sequence by using multiplexer 213 toconnect each of the N receive electrodes to demodulation circuit 216 insequence.

The mutual capacitance associated with each intersection between a TXelectrode and an RX electrode can be sensed by selecting every availablecombination of TX electrode and an RX electrode using demultiplexer 212and multiplexer 213. To improve performance, multiplexer 213 may also besegmented to allow more than one of the receive electrodes in matrix 225to be routed to additional demodulation circuits 216. In an optimizedconfiguration, wherein there is a 1-to-1 correspondence of instances ofdemodulation circuit 216 with receive electrodes, multiplexer 213 maynot be present in the system.

When an object, such as a finger, approaches the electrode matrix 225,the object causes a change in the measured mutual capacitance betweenonly some of the electrodes. For example, if a finger is placed near theintersection of transmit electrode 222 and receive electrode 223, thepresence of the finger will decrease the charge coupled betweenelectrodes 222 and 223. Thus, the location of the finger on the touchpadcan be determined by identifying the one or more receive electrodeshaving a decrease in measured mutual capacitance in addition toidentifying the transmit electrode to which the TX signal 224 wasapplied at the time the decrease in capacitance was measured on the oneor more receive electrodes.

By determining the mutual capacitances associated with each intersectionof electrodes in the matrix 225, the presence and locations of one ormore conductive objects may be determined. The determination may besequential, in parallel, or may occur more frequently at commonly usedelectrodes.

In alternative embodiments, other methods for detecting the presence ofa finger or other conductive object may be used where the finger orconductive object causes an increase in measured capacitance at one ormore electrodes, which may be arranged in a grid or other pattern. Forexample, a finger placed near an electrode of a capacitive sensor mayintroduce an additional capacitance to ground that increases the totalcapacitance between the electrode and ground. The location of the fingercan be determined based on the locations of one or more electrodes atwhich a change in measured capacitance is detected.

The induced current signal 227 is integrated by demodulation circuit216. The rectified current output by demodulation circuit 216 can thenbe filtered and converted to a digital code by ADC 217.

A series of such digital codes measured from adjacent sensor orintersections may be converted to touch coordinates indicating aposition of an input on touch sensor array 121 by touch coordinateconverter 218. The touch coordinates may then be used to detect gesturesor perform other functions by the processing logic 102.

In one embodiment, the capacitance sensor 101 can be configured todetect multiple touches. One technique for the detection and locationresolution of multiple touches uses a two-axis implementation: one axisto support rows and another axis to support columns. Additional axes,such as a diagonal axis, implemented on the surface using additionallayers, can allow resolution of additional touches.

FIG. 3A illustrates an embodiment of a capacitive touch sensing system300 that includes a capacitive sensor array 320. Capacitive sensor array320 includes a plurality of row sensor electrodes 331-340 and aplurality of column sensor electrodes 341-348. The row and column sensorelectrodes 331-348 are connected to a processing device 310, which mayinclude the functionality of capacitance sensor 101, as illustrated inFIG. 2. In one embodiment, the processing device 310 may perform TX-RXscans of the capacitive sensor array 320 to measure a mutual capacitancevalue associated with each of the intersections between a row sensorelectrode and a column sensor electrode in the sensor array 320. Themeasured capacitances may be further processed to determine higherresolution locations of one or more contacts at the capacitive sensorarray 320.

In one embodiment, the processing device 310 is connected to a host 150which may receive the measured capacitances or calculate high precisionlocations from the processing device 310.

The sensor array 320 illustrated in FIG. 3A includes sensor electrodesarranged in a diamond pattern. Specifically, the sensor electrodes331-348 of sensor array 320 are arranged in a single solid diamond (SSD)pattern. FIG. 3B illustrates a capacitive sensor array 321 having analternate embodiment of the diamond pattern, which is the dual soliddiamond (DSD) pattern. Each of the sensor electrodes of capacitivesensor array 321 includes two rows or columns of electrically connecteddiamond shaped traces. Relative to the SSD pattern, the DSD pattern hasimproved signal disparity characteristics due to an increase in thecoupling between TX and RX sensor electrodes while maintaining the sameself-capacitance coupling possible between each sensor electrode and aconductive object near the sensor electrode. The DSD pattern may alsoprovide higher sensitivity for tracking smaller objects, such as thepoint of a stylus, as compared to patterns having larger features, suchas SSD. However, the DSD pattern also increases the number of bridges(such as bridge 323) used to create the pattern, which may result indecreased manufacturing yield. The increased number of bridges may alsobe visible if metal bridges are used. For example, sensor array 321includes four bridges within unit cell 322.

As illustrated in FIG. 4A, one embodiment of a sensor array may beconstructed which has a first region having a diamond pattern, such as aSSD or DSD pattern, and a second region having a pattern different fromthe diamond pattern. For example, the second region may have a combpattern.

In one embodiment, the capacitive sensor array 400 may include a firstset of column sensor electrodes 401-408 each intersecting with each of asecond set of row sensor electrodes 411-418 to form a number of unitcells, such as unit cells 421, 431, and 432. Each of the unit cellscorresponds to a pair of sensor electrodes including a row sensorelectrode and a column sensor electrode. For example, unit cell 421corresponds to the pair of sensor electrodes 402 and 416.

In one embodiment, each point within a particular unit cell is nearer toa gap between the corresponding pair of sensor electrodes than to a gapbetween any other pair including a row and a column sensor electrode.For example, each point within unit cell 421 is nearest to a gap betweensensor electrode 402 and sensor electrode 416. Thus, the unit cell 421encloses an area where a finger or other conductive object may moststrongly affect the mutual capacitance between sensor electrodes 402 and416.

In one embodiment, a first trace pattern within a first unit cell may bedifferent from a second trace pattern within an adjacent unit cell. Forexample, the trace pattern within the unit cell 431 (which is associatedwith sensor electrodes 401 and 416) is different from the trace patternwithin the adjacent unit cell 421. The trace pattern within each ofthese unit cells refers to the pattern of conductive material that makesup the portions of sensor electrodes within the unit cells.

In one embodiment, the area of the capacitive sensor array 400 may bedivided into regions, where each unit cell in the same region containssubstantially the same trace pattern. In one embodiment, at least one ofthe regions, such as edge region 430, may be located at an edge of thecapacitive sensor array 400, while a core region 420 is located at thecenter of the sensor array 400. In one embodiment, the edge region 430may partially or completely surround the core region 420, and mayinclude some or all of the unit cells that are located at an edge of thesensor array 400. The edge region 430 includes edge unit cells such asunit cell 431 and corner unit cell 432, which include similar tracepatterns.

In one embodiment, the trace patterns within the unit cells of region430 may resemble two combs having interleaved teeth, with one comb-liketrace forming a portion of a row sensor element and the other comb-liketrace forming a portion of a column sensor element. This comb patternsubstantially differs from the single solid diamond (SSD) pattern of theunit cells within the core region 420, such as unit cell 421.

In one embodiment, the differences between the unit cell trace patternsof the different regions are substantially different; for example, thedifferences between the trace patterns may be greater than what may beattributable to manufacturing tolerances. In one embodiment, the tracepatterns between different regions may differ by other characteristics.

In one embodiment, a first trace pattern of a unit cell in a firstregion may differ from a second trace pattern of a unit cell in anadjacent region by the number of terminal branches that terminate withinthe unit cell. Comparing unit cell 431 with unit cell 421, for example,unit cell 431 includes four terminal branches for each portion of sensorelectrode within the unit cell 431, which is greater than the number ofterminal branches terminating within unit cell 421. In one embodiment, aterminal branch may be considered to be a conductive trace that branchesaway from a main trace of a sensor electrode and terminates.

In one embodiment, the trace pattern for the first unit cell may have alonger edge length than the trace pattern for the adjacent unit cell.For example, the length of the edges of the traces within unit cell 431may be longer than the edges of the traces within the adjacent unit cell421.

In one embodiment, the boundary length between the portions of thesensor electrodes within a first unit cell in the first region may belonger than the boundary length between the portions of the sensorelectrodes within a unit cell in the adjacent region. The boundarylength between portions of two electrodes may be considered to be thelength of the edges of the electrodes that face each other.

In one embodiment, the unit cells in one region may be smaller or largerin area than the unit cells in another region. For example, the edgeunit cell 431 may enclose a smaller area than the unit cell 421. In oneembodiment, each of the smaller unit cells may be less than or equal toapproximately 80% of the size of one of the larger unit cells. Forexample, each of the cells in the edge region 430 may be 80% of thesize, in area, of one of the unit cells in the core region 420.

In one embodiment of a capacitive sensor array, the unit cells in thecore may have X and Y dimensions of 5×5 mm, the corner unit cells mayhave dimensions of 4×4 mm, and 4×5 mm and 5×4 mm for the edges of thesensor along the Y axis and X axis, respectively.

In one embodiment, the geometries of the conductive traces in the unitcells may have other differing characteristics, including but notlimited to the average distance between the different sensor electrodes(as seen in unit cells 421 and 431), the area of the conductive materialenclosed within the unit cell, or the number of ear or mouth vertexes ofthe conductive traces within the unit cell.

In one embodiment, the differences between the unit cell trace patternsof the different regions may result in different capacitances betweenthe corresponding pairs of sensor electrodes. For example, a capacitanceCM1 attributable to the portions of the sensor electrodes within a unitcell in a first region may be greater or less than a capacitance CM2attributable to the portions of the sensor electrodes within a unit cellin a second region due to the different trace patterns within the unitcells. More specifically, the edge unit cell 431 includes portions ofsensor electrodes 401 and 416; the capacitance CM1 between the portionsof electrodes 401 and 416 within the unit cell 431 may be greater than acapacitance CM2 between the portions of electrodes 402 and 416, whichare within the unit cell 421 in an adjacent region.

In one embodiment, the responsiveness of the unit cell, measured as achange in capacitance ACM (between a capacitance measured when aconductive object is present and a capacitance measured when aconductive object is not present), may also differ between unit cells ina first region and unit cells in the adjacent region, as a result ofdifferent trace geometries in the unit cells. For example, unit cells inan edge region may have a greater ACM than unit cells in a core regionof the capacitive sensor array.

In one embodiment, the unit cells in different regions may, despitehaving different trace patterns or dimensions, still have similar CM andACM values. In one embodiment, the smaller unit cells, such as those inan edge region, may have CM or ACM values that are maximized by thetrace pattern to approximate or even exceed the CM and ACM values of theunit cells in the core region.

One embodiment of a capacitive sensing system configured to acquirecapacitance measurements from the capacitive sensor array 400 mayinclude firmware for compensating for this difference in capacitance forthe unit cells in different regions. In one embodiment, thiscompensation may be accomplished with a baseline compensation scheme,using a table of calculated or empirically determined calibrationvalues.

With reference to FIG. 4A, the terminal branches of the row and columnsensor electrodes within the edge region 430 are perpendicular to a nearedge of the capacitive sensor array 400. In an alternative embodiment ofa capacitive sensor array 450, the terminal branches are parallel to anear edge of the sensor array 450.

In one embodiment, the terminal branches for all unit cells in the edgeregion may be oriented along the same axis. For example, the terminalbranches of all unit cells in the edge region may be parallel to eachother, and may be aligned along the X axis, the Y axis, or not alignedto either axis.

With reference to FIG. 4A, the terminal branches of edge electrodes suchas electrode 401 and 411 are each connected to a main trace which has aportion within each of the unit cells through which the edge electroderuns. As illustrated in FIG. 4A, the main trace for these edge traces ispositioned at the edge of the sensor array 400 so that no part of theedge electrode overlaps a part of another sensor electrode.

In contrast, the sensor array 450 in FIG. 4B has edge electrodes with amain trace that is positioned away from the edge of the sensor array450. Thus, the main traces of the edge electrodes, such as electrode451, may overlap other sensor electrodes within the unit cells throughwhich the main traces pass, at intersections such as intersection 452.In one embodiment, a bridge may be used to cross over portions of othersensor elements at these intersections.

FIG. 5 illustrates an embodiment of a capacitive sensor array 500 havinga core region 520 surrounded by an edge region 510. In one embodiment,the shaded sensor electrodes are transmit (TX) sensor electrodes and theunshaded electrodes are receive (RX) sensor electrodes. The unit cellswithin the core region 520 have a comb-like trace pattern, where thesensor electrodes in the pair of electrodes corresponding to the unitcell are shaped like combs having interleaved teeth. The unit cellswithin the edge region 510 have a square spiral pattern, with theelectrodes intertwined in a spiral shape. In one embodiment, the ACMvalue of each unit cell in the edge region having the spiral shapedtrace pattern may be greater than a ACM value for any of the unit cellsin the core region.

In one embodiment, the difference in CM between the spiral pattern inthe edge region and the comb pattern in the core region may becompensated using a baseline compensation scheme. For example, the unitcells in the edge region may have a larger capacitance CM than the coreregion unit cells having a comb pattern; thus, a compensation currentmay be added or subtracted from an integration node to offset thedifference in baseline capacitance.

In one embodiment, the dimensions of various parts of the spiral, suchas the trace widths and distances between traces may be varied toachieve CM or ACM values for the unit cell that are equal to or higherthan the CM or ACM values for unit cells in the core region 520.

In one embodiment, the unit cells in the core region and the edge regionmay have different dimensions. For example, the unit cells in the coreregion 520 may have X and Y dimensions of 5×5 mm, the corner unit cellsmay have dimensions of 4×4 mm, and 4×5 mm and 5×4 mm for the edges ofthe sensor along the Y axis and X axis, respectively.

FIG. 6 illustrates an embodiment of a capacitive sensor array 600comprising TX row sensor electrodes 611-618 and RX column sensorelectrodes 621-628. Each of the row sensor electrodes 611-618 are formedfrom a single wide rectangular trace. The sensor electrodes 621-628 eachinclude three thinner main traces parallel to each other. Each of thesensor electrodes 621-628 intersects with each of the sensor electrodes611-618 to form a number of unit cells.

In one embodiment, the shape of the TX electrodes 611-618 performs ashielding function by collectively covering most of the area of thesensor array 600. However, the RX senor elements 621-628 may still bemodified so that unit cells located in different regions containdifferent trace patterns. For example, the unit cells in the edge region640 each have a different trace geometry than the unit cells in the coreregion 630. In one embodiment, the unit cells in the edge region mayhave additional connecting traces that connect the main traces togetherin parallel.

FIGS. 7A-7H illustrate various embodiments of trace patterns that may beused to construct sensor elements for capacitive sensor 600, asillustrated in FIG. 6. In one embodiment, any of the trace patterns700-707 may be used at the ends of the RX sensor electrodes, such assensor electrode 624.

FIG. 7A, 7B, and 7C illustrate embodiments of a trace pattern thatinclude a number of cutout areas, or windows formed by connecting tracesbetween main traces of the trace pattern. Trace pattern 701, forexample, includes main traces 701 b which are connected together byconnecting traces 701 c. This trace pattern forms cutout areas 701 a inthe spaces between the main traces 701 b and the connecting traces 701c. Trace patterns 700 and 702 also have cutout areas, but may have moreor fewer cutout areas formed by correspondingly more or fewer connectingtraces.

FIG. 7D, 7E, and 7F illustrate embodiments of trace patterns thatinclude main traces and connecting traces, similar to trace patterns700-702, and also include sets of terminal branches extending away fromeither the connecting traces or the main trace. For example, tracepattern 703 includes three main traces 703 b connected by threeconnecting traces, including connecting trace 703 c. Terminal branches703 a extend from connecting trace 703 c into the cutout areas formed inthe spaces between the main traces 703 b and the connecting traces.

In FIG. 7E, trace pattern 704 is similar to pattern 703 except that theterminal branches 704 a extend from the central main trace. In FIG. 7F,trace pattern 705 also includes terminal branches that extend from acentral main trace, but has fewer connecting traces.

FIG. 7G illustrates an embodiment of a trace pattern that includestriangular cutout areas 706 c formed in the space between connectingtrace 706 a and diagonally oriented connecting traces 706 b.

FIG. 7H illustrates an embodiment of a trace pattern that includes asingle large cutout area 707 a formed in the space between the maintraces 707 b and connecting traces 707 c.

FIGS. 7I-7N illustrate embodiments of trace patterns that, similar totrace patterns 700-707, may be used in constructing the RX sensorelectrodes of capacitive sensor array 600.

Trace patterns 708-710 each comprise three main traces, along withterminal branches extending from the main traces. Trace pattern 708includes two terminal branches, such as branches 708 a, extending fromeither side of each main trace. In one embodiment, the positions ofthese terminal branches may be staggered. Trace pattern 709 includesthree main traces. The outer main traces, such as main trace 709 a, areeach connected to multiple pairs of terminal branches, such as branches709 b, extending away from the main trace. In trace pattern 710, a pairof terminal branches extend away from the central main trace 710 a,while a single terminal branch extends away from one side of each of theouter main traces.

FIGS. 7L-7N illustrate trace patterns where the main traces are formedin wave shapes. Trace pattern 711 includes main traces 711 a that areshaped in a half sine wave pattern near the end of the sensor electrode.In trace pattern 712, the main traces 712 a each have a singletriangular wave pattern, while in trace pattern 713, the main traces 713a each have a double triangular wave pattern.

FIG. 8 illustrates an embodiment of a capacitive sensor array 800 havingan edge region 820 containing unit cells that are half the size of unitcells in a core region 810. Additionally, two main traces make up theportions of the RX column sensor electrodes in the core region 810,while in the edge region 820, the portions of the RX column sensorelectrodes include an additional third trace extending from a connectingtrace. For example, the portions of sensor electrode 804 in the coreregion 810 include the two main traces 801. In the edge region 820, thesensor electrode 804 has an additional trace 802 branching away from theconnecting trace 803.

In one embodiment, the widths of the traces in the core region 810 maydiffer from the widths of the traces in the edge region 810. In oneembodiment, the traces in the core region 810 may be 0.4 mm, while thetraces in the edge region 820 are 0.55 mm. In one embodiment, the edgeregion unit cells may have the approximately the same CM as the coreregion unit cells. In an alternative embodiment, the edge region unitcells may have a greater CM than the core region unit cells.

As illustrated in FIG. 8, the RX column sensor electrode 805 may includea number of terminal branches that are perpendicular relative to thetraces of other sensor electrodes. Furthermore, in this arrangement, thesensor electrode 805 in the corner unit cell partially overlaps withneighboring unit cells. In one embodiment, the baseline capacitance CMof the corner cell in the layout may be close to the CM values for theother unit cells in the sensor array 800.

In one embodiment, the sensor electrode 805 may have a single main traceto connect a number of terminal branches, and this main trace may belocated at the edge of the sensor array 800. In one embodiment, sincethe main trace is at the edge of the sensor array 800, it may beconstructed from metal without becoming a conspicuous visual feature.For example, a metal main trace at the edge of the sensor array 800 maybe located outside of a visible area if the sensor array 800 is used inan application such as a touch screen display.

FIG. 9 illustrates an embodiment of a capacitive sensor array 900 whichlacks a corner unit cell. In sensor array 900, the majority of thecorner area is instead divided along the diagonal between the twoadjacent edge unit cells. Thus, a finger or other conductive object inthe corner area will affect the mutual capacitances of the electrodepairs 911:902 and 912:901, which are associated with the adjacent edgeunit cells nearest to the corner.

FIGS. 10A and 10B illustrate embodiments of capacitive sensor arrays1000 and 1050 having three main traces per RX sensor electrode andshielding TX sensor electrodes. In capacitive sensor array 1000, thesensor electrodes may be made purely of ITO; thus, sensor resistance maybe higher for the farthest unit cell 1002 than for other unit cells,resulting in a higher RC delay when transmitting or receiving a signal.Reduction of this RC delay may be achieved by decreasing the resistanceof the sensor electrodes associated with unit cell 1002.

In one embodiment, capacitive sensor array 1050, illustrated in FIG.10B, may include sensor electrodes which are primarily made from amaterial such as Indium Tin Oxide (ITO); however, in contrast with thecorresponding sensor electrode 1001 of sensor array 1000, the resistanceof sensor electrode 1052 may be reduced by including a metal striprunning along an edge of the electrode 1052, which is also along theedge of the capacitive sensor array 1050. In this location, the metalstrip 1051 may be located outside a visible area of the sensor array1050, for example, if the capacitive sensor array 1050 is used in atouch screen display. Thus, the trace pattern for the unit cells in theedge region 1053 differ from the trace patterns of unit cells in otherregions, which do not include the metal strip.

In one embodiment, a metal strip may be applied to sensor electrodes inboth the X and Y directions, as illustrated in FIG. 10C. The TX sensorelectrode 1071 includes a metal strip 1071 at the edge of the sensorarray 1070, while the RX sensor electrode also includes a metal strip1072 along another edge of the sensor array 1070. In one embodiment, themetal strip 1072 electrically connects portions of the sensor electrode1074. In one embodiment, the metal strips in sensor arrays 1050 and 1070may reduce the resistance of the sensor electrodes to which they areapplied. In one embodiment, the metal strips may extend for less thanthe entire length of the sensor electrode, such that the sensorelectrode may be designed to have a specific resistance.

In one embodiment, the application of metal features at an edge of asensor array may also be applied to a sensor array having a diamondpattern, as illustrated with reference to FIGS. 11A and 11B.

FIG. 11A illustrates a capacitive sensor array 1100, where a sensorelectrode 1101 in an edge region of the sensor array 1100 includes fiveportions that are electrically connected by bridges 1102, which are madefrom conductive material such as metal. In contrast with sensorelectrode 1101, the portions of sensor electrode 1151 in sensor array1150, as illustrated in FIG. 11B, are connected by a metal strip 1152and metal connecting traces 1153, with each of the connecting traces1153 connecting the metal strip 1152 to one of the portions of thesensor electrode 1151.

FIG. 12 illustrates an embodiment of a capacitive sensor array 1200where a metal strip 1201 is used to reduce the resistance of a sensorelectrode 1202 having a “totem pole” pattern, with several terminalbranches extending away from a single main trace. In one embodiment, themetal strip 1201 may connect to the ends of traces extending from themain trace to provide an additional conductive path for current flowingthrough the sensor electrode 1202. The metal strip may be located at anedge of the sensor array 1200.

In the foregoing embodiments, various modifications can be made; forexample, row sensor electrodes and column sensor electrodes may beinterchanged, and row or column sensor electrodes may be used as eitherTX or RX sensor electrodes. Furthermore, in some embodiments,intersections between row and column sensor electrodes may be replacedwith conductive bridges. For example, bridges may be used toelectrically connect portions of sensor electrodes when both row andcolumn sensor electrodes are constructed from a single layer ofconductive material. As described herein, conductive electrodes that are“electrically connected” or “electrically coupled” may be coupled suchthat a relatively low resistance conductive path exists between theconductive electrodes.

Embodiments of the present invention, described herein, include variousoperations. These operations may be performed by hardware components,software, firmware, or a combination thereof. As used herein, the term“coupled to” may mean coupled directly or indirectly through one or moreintervening components. Any of the signals provided over various busesdescribed herein may be time multiplexed with other signals and providedover one or more common buses. Additionally, the interconnection betweencircuit components or blocks may be shown as buses or as single signallines. Each of the buses may alternatively be one or more single signallines and each of the single signal lines may alternatively be buses.

Certain embodiments may be implemented as a computer program productthat may include instructions stored on a computer-readable medium.These instructions may be used to program a general-purpose orspecial-purpose processor to perform the described operations. Acomputer-readable medium includes any mechanism for storing ortransmitting information in a form (e.g., software, processingapplication) readable by a machine (e.g., a computer). Thecomputer-readable storage medium may include, but is not limited to,magnetic storage medium (e.g., floppy diskette); optical storage medium(e.g., CD-ROM); magneto-optical storage medium; read-only memory (ROM);random-access memory (RAM); erasable programmable memory (e.g., EPROMand EEPROM); flash memory, or another type of medium suitable forstoring electronic instructions.

Additionally, some embodiments may be practiced in distributed computingenvironments where the computer-readable medium is stored on and/orexecuted by more than one computer system. In addition, the informationtransferred between computer systems may either be pulled or pushedacross the transmission medium connecting the computer systems.

Although the operations of the method(s) herein are shown and describedin a particular order, the order of the operations of each method may bealtered so that certain operations may be performed in an inverse orderor so that certain operation may be performed, at least in part,concurrently with other operations. In another embodiment, instructionsor sub-operations of distinct operations may be in an intermittentand/or alternating manner.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will, however,be evident that various modifications and changes may be made theretowithout departing from the broader spirit and scope of the invention asset forth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense.

What is claimed is: 1-20. (canceled)
 21. A capacitive sensor arraycomprising: a first unit cell formed by a first intersection of a firstelectrode and a second electrode; and a second unit cell formed adjacentto the first unit cell and formed by a second intersection of the firstelectrode and a third electrode, wherein a first trace of the firstelectrode in the first unit cell has a first geometry, and a secondtrace of the first electrode in the second unit cell has a secondgeometry, the second geometry substantially dissimilar from the firstgeometry.
 22. The capacitive sensor array of claim 21, wherein the firstunit cell is formed in and edge region of the capacitive sensor array.23. The capacitive sensor array of claim 21, wherein the second unitcell is formed in a core region.
 24. The capacitive sensor array ofclaim 21, wherein: a third trace of the second electrode in the firstunit cell has a third geometry; and a fourth trace of the thirdelectrode in the second unit cell has a fourth geometry.
 25. Thecapacitive sensor array of claim 24, wherein the second geometry of thesecond trace and the fourth geometry of the fourth trace aresubstantially similar.
 26. The capacitive sensor array of claim 21,wherein a first mutual capacitance change by a presence of a conductiveobject in proximity to the first intersection is substantiallydissimilar from a second mutual capacitance change by the presence ofthe conductive object in proximity to the second intersection.
 27. Thecapacitive sensor array of claim 21, wherein the first trace of thefirst electrode comprises at least one branch disposed within the firstunit cell.
 28. the capacitive sensor array of claim 21, furthercomprising a fifth trace substantially parallel to the first trace and aconnecting trace coupling the first trace and the fifth trace, theconnective trace disposed within the first unit cell.
 29. A systemcomprising: a capacitive sensing circuit; a first electrode coupled tothe capacitive sensing circuit; a second electrode coupled to thecapacitive sensing circuit, the second electrode disposed substantiallyperpendicular to the first electrode, the first and second electrodesforming a first unit cell at a first intersection between the firstelectrode and the second electrode; and a third electrode coupled to thecapacitive sensing circuit, the third electrode disposed substantiallyperpendicular to the first electrode, the first and third electrodesforming a second unit cell at a second intersection between the firstelectrode and the third electrode, wherein: the first electrodecomprises a first trace having a first geometry within the first unitcell, the first electrode comprises a second trace having a secondgeometry within the second unit cell, the first and second geometriessubstantially dissimilar.
 30. The system of claim 29, wherein the firstunit cell is formed in and edge region of the capacitive sensor array.31. The system of claim 29, wherein the second unit cell is formed in acore region.
 32. The system of claim 29, wherein: the second electrodecomprises a third trace disposed within the first unit cell, the thirdtrace having a third geometry; and the third electrode comprises afourth trace disposed within the second unit cell, the fourth tracehaving a fourth geometry.
 33. The system of claim 32, wherein the secondgeometry of the second trace and the fourth geometry of the fourth traceare substantially similar.
 34. The system of claim 29, wherein the firsttrace of the first electrode comprises at least one branch disposedwithin the first unit cell.
 35. The system of claim 29, wherein thefirst electrode comprises a fifth substantially parallel to the firsttrace and a connecting trace coupling the first trace and the fifthtrace, the connective trace disposed within the first unit cell.
 36. Amethod comprising: forming a first electrode disposed forming a secondelectrode substantially perpendicular to the first electrode, wherein afirst intersection between the first electrode and the second electrodeidentifies a first unit cell; and forming a third electrodesubstantially perpendicular to the first electrode, wherein a secondintersection between the first electrode and the third electrodeidentifies a second unit cell, wherein a first trace of the firstelectrode in the first unit cell has a first geometry, and a secondtrace of the first electrode in the second unit cell has a secondgeometry, the second geometry substantially dissimilar from the firstgeometry.
 37. The method of claim 36, wherein the second electrode isforming within a edge region of the capacitive sensor array.
 38. Themethod of claim 36, wherein the third electrode is formed within a coreregion and at least one edge region.
 39. The method of claim 21,wherein: a third trace of the second electrode in the first unit cellhas a third geometry; and a fourth trace of the third electrode in thesecond unit cell has a fourth geometry.
 40. The method of claim 39,wherein the second geometry of the second trace and the fourth geometryof the fourth trace are substantially similar.